Structure, magnetic recording medium, and method of producing the same

ABSTRACT

To provide a filmy structure of a nanometer size having a phase-separated structure effective for the case where a compound can be formed between two kinds of materials. A structure constituted by a first member containing a compound between an element A except both Si and Ge and Si n Ge 1-n  (where 0≦n≦1) and a second member containing one of the element A and Si n Ge 1-n  (where 0≦n≦1), in which one of the first member and the second member is a columnar member, formed on a substrate, whose side face is surrounded by the other member, the ratio Dl/Ds of an average diameter Dl in the major axis direction to an average diameter Ds in the minor axis direction of a transverse sectional shape of the columnar member is less than 5, and the element A is one of Li, Na, Mg, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Rb, Sr, Y, Zr, Nb, Mo, Ru, Rh, Pd, Cs, Ba, La, Hf, Ta, W, Re, Os, Ir, Pt, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and B.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a structure of a nanometer size havinga phase-separated structure or a structure obtained from such material.Furthermore, the present invention relates to a method of producing suchstructure and a device constituted of such structure such as anelectronic device, an electrode, a magnetic recording medium, afunctional film having catalytic ability, or an electron emittingdevice.

2. Related Background Art

There has been a growing interest in a fine structure as a functionalmaterial in recent years. An example of an approach to produce such finestructure includes an approach to produce a fine structure directly bymeans of a semiconductor processing technique typified by a fine patternforming technique such as photolithography.

In addition to the above semiconductor processing technique, an approachto utilize a self-organization phenomenon or self-formation phenomenonof a material is available as a technique for producing a finestructure. This approach intends to realize a novel fine structure onthe basis of a regular structure to be spontaneously formed. Out of theapproaches of this kind, one disclosed in the US Published ApplicationUS-2005-0053773 involves forming a phase-separated structure between afirst material and a second material, so a self-organized structure canbe formed of an inorganic material.

The production of a structure as described in the above US PublishedApplication has been considered to require that no compound between thefirst material and the second material be formed (for example, betweenaluminum and silicon). In this case, only several combinations ofselectable materials are available. Therefore, there has been a demandon the ability to form a self-organizing phase-separated structure evenin a combination of materials capable of forming a compound as well assuch limited combinations of materials.

SUMMARY OF THE INVENTION

In view of the foregoing, an object of the present invention is toprovide a structure of a nanometer size having a phase-separatedstructure which is effective for the case where a compound between twokinds of materials can be formed and a method of producing thestructure.

In particular, an object of the present invention is to provide astructure of a nanometer size having, when a compound can be formedbetween Si_(n)Ge_(1-n) (where 0≦n≦1) and an element A except both Si andGe, an effective phase-separated structure composed of the compoundbetween the element A and Si_(n)Ge_(1-n) (where 0≦n≦1) and the element Aor Si_(n)Ge_(1-n) (where 0≦n≦1) and a method of producing the structure.

Another object of the present invention is to provide a structureobtained by removing a material constituting one phase from suchstructure having a phase-separated structure as described above.

Another object of the present invention is to provide various deviceseach constituted of such structure as described above.

In view of the foregoing, the present invention provides a structureincluding:

a first member containing a compound between an element A except both Siand Ge and Si_(n)Ge_(1-n) (where 0≦n≦1); and

a second member containing one of the element A and Si_(n)Ge_(1-n)(where 0≦n≦1),

in which

one of the first member and the second member is a columnar member whoseside face is surrounded by the other member;

the ratio Dl/Ds of an average diameter Dl in the major axis direction toan average diameter Ds in the minor axis direction of a transversesectional shape of the columnar member is less than 5; and

the element A is one of Li, Na, Mg, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co,Ni, Cu, Rb, Sr, Y, Zr, Nb, Mo, Ru, Rh, Pd, Cs, Ba, La, Hf, Ta, W, Re,Os, Ir, Pt, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and B.

According to the present invention, there is provided a structure of ananometer size having a phase-separated structure even when a compoundcomprised of two kinds of materials can be formed. In particular,according to the present invention, there is provided a structure of ananometer size having, when a compound can be formed betweenSi_(n)Ge_(1-n) (where 0≦n≦1) and an element A except both Si and Ge, aphase-separated structure composed of the compound between the element Aand Si_(n)Ge_(1-n) (where 0≦n≦1) and the element A or Si_(n)Ge_(1-n)(where 0≦n≦1). Removing a material constituting one phase from thestructure having a phase-separated structure provides a porous structureor a needle-like structure. Various devices each using any one of thosestructures are also provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are schematic views each showing a structure of thepresent invention;

FIG. 2 is a flow chart concerning a method of specifying the structureof the present invention from the ratio of an average diameter in amajor axis direction to an average diameter in a minor axis direction;

FIGS. 3A and 3B are schematic views each showing a diameter in a majoraxis direction and a diameter in a minor axis direction in the structureof the present invention;

FIGS. 4A, 4B, 4C and 4D each show an example of an equilibrium diagrampossessed by a raw material constituting each of a conventionalstructure and the structure of the present invention;

FIGS. 5A and 5B are conceptual views each showing a process for forminga phase-separated structure;

FIGS. 6A and 6B are schematic views each showing a porous structure ofthe present invention;

FIGS. 7A and 7B are schematic views each showing a needle-like structureof the present invention;

FIG. 8 is a schematic view showing the layer constitution of a magneticrecording medium;

FIGS. 9A and 9B are schematic views each showing an example of amagnetic recording medium using the structure of the present invention;

FIGS. 10A and 10B are schematic views each showing an example of arecording layer using the porous structure of the present invention;

FIGS. 11A and 11B are schematic views each showing an example of a softmagnetic layer using the porous structure of the present invention;

FIG. 12 is a schematic view showing a magnetic recording/reproducingdevice using a magnetic recording medium of the present invention;

FIG. 13 is a conceptual view of an information processing system using amagnetic recording/reproducing device of the present invention;

FIG. 14 is a conceptual view showing an example of an electronic deviceusing the structure of the present invention;

FIGS. 15A and 15B are schematic views each showing an electrode portionof a transistor;

FIGS. 16A and 16B are schematic views each showing a functional filmhaving catalytic ability using the porous structure of the presentinvention;

FIGS. 17A and 17B are schematic views each showing a functional filmhaving catalytic ability using the needle-like structure of the presentinvention;

FIGS. 18A and 18B are conceptual views each showing an electron emittingdevice using the structure of the present invention;

FIGS. 19A and 19B are conceptual views each showing an electron emittingdevice using the needle-like structure of the present invention; and

FIG. 20 is a conceptual view for explaining a sputtering method.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The structure and method of producing a structure of the presentinvention, the concept of the formation of a structure, and the likewill be described in detail with reference to the drawings. Furthermore,an electronic device, a gate electrode for a semiconductor integratedcircuit, a magnetic recording medium, a functional film having catalyticability, and an electron emitting device according to the presentinvention will be described.

[Structure]

FIGS. 1A and 1B each show a schematic view of the structure of thepresent invention. FIG. 1A is a plan view, and FIG. 1B is a sectionalview taken along the line 1B-1B of FIG. 1A.

The structure is of a film shape formed on the surface of a substrate104.

That is, the structure includes a first member containing a compoundbetween an element A, capable of forming a compound between the elementA and Si_(n)Ge_(1-n) (where 0≦n≦1), and Si_(n)Ge_(1-n) (where 0≦n≦1) anda second member containing one of Si_(n)Ge_(1-n) (where 0≦n≦1) and theelement A.

Si_(n)Ge_(1-n) (where 0≦n≦1) represents Si when n=1, Ge when n=0, or asubstance containing Si and Ge when 0≦n≦1 (hereinafter, the substancemay be abbreviated as SiGe). One of the first and second members is acolumnar member, and the columnar member is formed so as to besubstantially perpendicular to the surface of the substrate 104 (or aninterface between the film formed on the substrate and constituted bythe first and second members and the substrate).

The element A is one of Li, Na, Mg, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co,Ni, Cu, Rb, Sr, Y, Zr, Nb, Mo, Ru, Rh, Pd, Cs, Ba, La, Hf, Ta, W, Re,Os, Ir, Pt, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and B.

In a first combination 103, a first member 100 mainly containing “acompound between the element A and Si_(n)Ge_(1-n) (where 0≦n≦1)” such asPdSi, PdGe, or PdSiGe is the columnar member. The side face of firstmember 100 is surrounded by a second member 101 mainly containingSi_(n)Ge_(1-n) (where 0≦n≦1) such as Si, Ge, or SiGe. A plurality ofsuch first members are dispersedly arranged in the structures material.In a second combination 102, a second member 101′ mainly containingSi_(n)Ge_(1-n) (where 0≦n≦1) such as Si, Ge, or SiGe is a columnarmember. The side face of the second member 101′ is surrounded by a firstmember 100′ mainly containing “a compound between the element A andSi_(n)Ge_(1-n) (where 0≦n≦1)” such as PdSi, PdGe, or PdSiGe. A pluralityof such second members are dispersedly arranged in the structuresmaterial. In an actual structure, one of the first combination 103 andthe second combination 102 is realized.

The columnar member 100 or 101′ extend in a film thickness direction,that is, substantially perpendicular to the surface of the substrate104. The transverse sectional shape of the member is nearly constantirrespective of position in the film thickness direction. Therefore, thetransverse sectional shape of a filmy structure is substantiallyidentical to the shape of the upper end face of the columnar member 100or 101′ forming a main surface opposite to the substrate. In FIGS. 1Aand 1B, the upper end face of the columnar member 100 or 101′ is of acircular shape. However, the shape is not limited to the circular shape.The shape may be an elongated elliptical shape, or further elongated andbent structure. However, the upper end face of the columnar member 100or 101′ is preferably of a circular shape, and a variation in size amongplural columnar members is preferably small. In this case, inparticular, the standard deviation of the diameters of the columnarmembers is preferably 3 nm or less, or more preferably 2 nm or less. Theterm “transverse sectional shape” refers to a shape when the film formedon the substrate and constituted by the first and second members is seenfrom the direction perpendicular to an interface between the film andthe substrate. That is, the term refers to the plan shape of the filmwhen the film is formed on the substrate.

In FIGS. 1A and 1B, the columnar member 100 or 101′ is regularlyarranged in a honeycomb fashion. However, the arrangement is not limitedthereto. However, when a filmy structure is formed on the substrate 104in a non-equilibrium state by means of such sputtering method asdescribed later, a honeycomb arrangement tends to be formed in aself-organization manner in a region where a film to be formed has asufficient thickness. In addition, the regular arrangement of thecolumnar member 100 or 101′ is maintained in a certain region, so theregularity may be disordered at a boundary between different regions.

In the present invention, the ratio Dl/Ds of an average diameter Dl inthe major axis direction to an average diameter Ds in the minor axisdirection of a transverse sectional shape (or end face shape) of thecolumnar member 100 or 101′ is less than 5. As shown in FIG. 3A, when nocolumnar member having a bent portion in its transverse sectional shape(or end face shape) is present, the major axis direction and the minoraxis direction in the transverse sectional shape (or end face shape) ofa columnar member are clearly recognized, and a diameter 300 in themajor axis direction and a diameter 301 in the minor axis direction areeasily defined. However, the definition is complicated in case of acolumnar member having a bent portion as shown in FIG. 3B. The diameter301 in the minor axis direction can be defined at an arbitrary positionwith a short segment in the transverse sectional shape (or end faceshape) of a columnar member as a width because the widths of pluralcolumnar members are relatively constant. However, the diameter in themajor axis direction cannot be calculated by drawing a straight line. Inthis case, the following procedure is effective. A bent portion in thetransverse sectional shape (or end face shape) of a columnar member iselongated to be approximately regarded as an elongated rectangle tocalculate the diameter 300 in the major axis direction.

Here, a method of determining whether a structure satisfies therelationship of [average diameter Dl in major axis direction]/[averagediameter Ds in minor axis direction]<5 will be described with referenceto the flow chart shown in FIG. 2.

(a) At first, the surface of the structure of the present invention isobserved with an electron microscope so that an image with which theshape of the upper end face of a columnar member can be identified isobtained. At this time, the structure may be observed unclearly with ascanning electron microscope depending on an element constitution.Therefore, the image may be obtained by means of not only imageformation by a secondary electron from an upper end face but also imageformation by a transmission electron with the aid of a transmissionelectron microscope.

(b) The image obtained in the above step (a) is processed by means of anappropriate software for binarization. For example, (b) of FIG. 2 showstwo kinds of binarized images of a structure belonging to the presentinvention. Here, the structure is characterized in that it is difficultto establish the concept of a diameter for a columnar member having anelongated upper end face. In view of this, cases upon analysis wereclassified as described below.

[When No Columnar Member Having a Bent Portion is Present]

(c-1) A columnar member in the image binarized by means of an imageprocessing software is recognized, and each of the diameters in themajor axis direction and the minor axis direction is calculated.

[When a Large Number of Columnar Members Each Having a Bent Portion arePresent]

(c-2) Columnar members in the image binarized by means of an imageprocessing software are recognized, and the area of each columnar memberis calculated. Furthermore, it can be observed from the image that adiameter in a direction considered to be the minor axis direction issubstantially constant. Therefore, the average of diameters in the minoraxis direction of plural columnar members (average diameter in the minoraxis direction) is calculated. Then, the average of the values for therespective columnar members each calculated from the expression of [areaof columnar member]/[average diameter in minor axis direction] isapproximately defined as an average diameter in the major axisdirection. This corresponds to the condition that bent columnar membersare regarded as rectangles having the same length upon calculation.

(d) Next, with the respective calculated average diameters, theexpression of [average diameter Dl in major axis direction]/[averagediameter Ds in minor axis direction] is calculated.

(e) Finally, the structure is determined to be that of the presentinvention when the value obtained in the step (d) is less than 5.

In the present invention, the average diameter in the minor axisdirection of plural columnar members is in the range of, for example,0.5 nm to 20 nm (both inclusive). In addition, the average distancebetween centers of gravity in the transverse sectional shapes of eachcolumnar member and a columnar member closest to the each columnarmember is, for example, 30 nm or less.

[Method of Producing Structure]

A substrate for forming a filmy structure is prepared. The substrate 104is not particularly limited. For example, an insulating substratecomposed of an oxide (such as glass or quartz glass) or of plastic isusable. A semiconductor substrate composed of, for example, silicon,germanium, gallium arsenide, indium phosphide, or the like, or a metalsubstrate composed of aluminum or the like can also be used depending ona purpose. A substrate subjected to patterning by means of a resist orthe like is also usable. A material for the substrate 104 is not limitedto the foregoing.

Furthermore, a material individually or integrally containing an elementA and Si_(n)Ge_(1-n) (where 0≦n≦1) serving as a material constitutingthe structure is prepared. A material individually containing Si and Gemay be used for SiGe. That is, the structure always contains a compoundbetween the element A except both Si and Ge and Si_(n)Ge_(1-n) (where0≦n≦1). Accordingly, Si_(n)Ge_(1-n) (where 0≦n≦1) and the element Aneeds to be prepared as raw materials; provided, however, thatSi_(n)Ge_(1-n) (where 0≦n≦1) and the element A are not needed to beisolated from each other. Any one of the forms such as a form comprisinga compound between the element A and Si_(n)Ge_(1-n) (where 0≦n≦1) andthe element A, a form comprising a compound between the element A andSi_(n)Ge_(1-n) (where 0≦n≦1) and Si_(n)Ge_(1-n) (where 0≦n≦1), and amixture of the element A and Si_(n)Ge_(1-n) (where 0≦n≦1) is permitted.

A target structure can be obtained by depositing elements serving as rawmaterials on the substrate 104 in a non-equilibrium state using thosematerials. At this time, the elements serving as raw materials arepreferably quickly cooled on the substrate 104 with a view to forming astructure having an average diameter Ds in a minor axis direction ofcolumnar members in the range of 0.5 nm to 20 nm (both inclusive) and anaverage distance between centers of gravity of a columnar member and itsclosest columnar member of 30 nm or less. That is, the energy of theelements serving as raw materials is preferably lost quickly. It shouldbe noted that there is provided such a condition that surface diffusionoccurs in a time scale in which the phase-separated of the elementsserving as raw materials occurs. In such situation, a fine structurethat cannot be easily attained by means of a conventional approachattempted with bulk (an approach to dissolve the entirety followed byquenching and solidifying the resultant in one way) can be uniformlyformed in the direction in which the elements serving as raw materialsare deposited. Furthermore, the deposition in a non-equilibrium state ispreferably performed by means of a method to be performed in a vaporphase or a vacuum such as a sputtering method and an electron beamdeposition method, particularly preferably the sputtering method. FIG.20 shows a sputtering method. As shown in the figure, the substrate 104is arranged so as to be opposite to a sputtering target 2001 mainlycontaining a raw material. The sputtering target 2001 may be an alloy ora sintered material as long as it contains a required raw material.Alternatively, as shown in FIG. 20, one material may be arranged as atarget, and another material may be arranged as a plate having anarbitrary size on the target. For example, the sputtering target 2001 iscomposed of Si_(n)Ge_(1-n) (where 0≦n≦1), and a plate 2002 of a certainelement (element A) arranged on the central portion of the target iscomposed of Pd. Furthermore, in the sputtering, a raw material is causedto sputter from the sputtering target 2001 by means of a process gassuch as argon and is sequentially deposited on the substrate 104. Adeposition direction 2005 with respect to the substrate 104 to bearranged so as to be opposite to the target is a direction toward whichthe material deposits. Furthermore, the sputtering is an approacheffective in obtaining the structure of the present invention becausethe sputtering raw material has high energy, loses its energy quickly onthe substrate 104, and diffuses on the surface of the substrate to someextent. Therefore, the formation of a structure can be preciselycontrolled by means of, for example, a distance 2004 between thesputtering target and the substrate, input electric power, the kind andpressure of a process gas, the temperature of the substrate 104, and abias voltage to be applied to the substrate 104 in the sputteringmethod.

The structure of the present invention is based on the formation of astructure in a self-organization manner due to the mutual diffusion ofelements and the like serving as raw materials on the substrate 104. Ina situation where a deposition rate is excessively high, the elementsand the like serving as raw materials are sequentially deposited beforethe completion of phase separation, so the degree of phase separationtends to lower. Therefore, a slow deposition rate is effective forseparation. Increasing the distance 2004 between the sputtering targetand the substrate can sufficiently lower a deposition rate. However,when a distance up to the substrate 104 is excessively long, the energyof the elements and the like serving as raw materials to be depositedreduces before the elements and the like fly to the substrate 104. As aresult, even when the elements and the like have a time period fordiffusion on the substrate 104, they may have insufficient energy fordiffusion. In view of the foregoing, energy necessary for the rawmaterials flying to the substrate 104 to diffuse can be given byapplying a bias voltage to the substrate 104 or by increasing thetemperature of the substrate in such situation. Therefore, appropriatelymaintaining deposition conditions is preferable for forming thestructure of the present invention in consideration of the foregoing.

Finally, the structure of the present invention is applicable to thesurface of the substrate 104 of any type in addition to the aboveexamples, and some condition to cause no damage to the substrate 104under the respective forming conditions may be present. In addition, thethickness of the structure as a film can be increased without anylimitation by lengthening a deposition time. However, the kind of thesubstrate 104, the kind of an underlayer to be formed as desired as thesurface layer of the substrate, and the like are preferablyappropriately selected in consideration of the appropriate control of astress or the like to be generated in a film to be formed.

[Concept of Formation of Structure and the Like]

The formation of the structure of the present invention will beadditionally described.

Proposals concerning the formation of a nano-scale structure utilizingself-organization on the basis of an inorganic material have beenconventionally rarely made.

However, as described above, a phase-separated structure mainly usingaluminum and silicon has been proposed. However, the proposal needs tohave a binary eutectic phase diagram over the entire compositional rangeas shown in FIG. 4A. Therefore, it can be found that the number ofcombinations of elements having such phase diagram is unexpectedlysmall.

Thus, the achievement of such structure by means of other combinationsof elements has been considered to be extremely difficult. That is, inthe case of a eutectic type over the entire compositional range in abinary system like the conceptual view shown in FIG. 5A, a phaseseparation process 504 of flying elements 501 (each in the form of anatom or the like) on a substrate surface 503 is expected to proceedsmoothly because no compound comprised of those binary elements isproduced.

However, in the case of a binary system phase diagram like FIG. 4B,plural formable compounds 401 are present, so it is expected to bedifficult for the formation of a compound on the substrate 104 toprogress simultaneously with phase separation. That is, the followingcan be easily conceived. Even in the case of a eutectic phase diagramlike FIG. 4C or 4D between a raw material element or the like and acompound, it is not apparent that such a phase separation process 504that elements 502 performing surface diffusion form a compound 505followed by additional agglomeration as in the conceptual view of FIG.5B will be sequentially caused.

However, the inventors of the present invention have made extensivestudies to find that phase separation between a raw material element orthe like and a compound thereof as shown in FIG. 4C or 4D can also beachieved by controlling deposition conditions in a non-equilibriumstate. Therefore, according to the present invention, a structure havinga nano-scale phase-separated structure can be formed by means of manymaterials that have been conventionally thought to be inapplicable.

The main characteristic of the present invention is a phase-separatedstructure between Si_(n)Ge_(1-n) (where 0≦n≦1) or an element A exceptboth Si and Ge and a compound between the element A and Si_(n)Ge_(1-n)(where 0≦n≦1). They may not be the eutectic type over the entirecompositional range between constituent elements and the like.

Accordingly, as for applicable materials, the element A is preferablyselected from Li, Na, Mg, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Rb,Sr, Y, Zr, Nb, Mo, Ru, Rh, Pd, Cs, Ba, La, Hf, Ta, W, Re, Os, Ir, Pt,Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and B.

However, any other element in addition to those described above may beused as the element A as long as the structure of the present inventioncan be formed of the element. In addition, another element than theabove raw materials is preferably added in an amount of 30 atomic % orless. The amount of the element except the above raw materials to beadded is more preferably 15 atomic % or less. In particular, the partialaddition of a material having a eutectic phase diagram over the entirecompositional range with Si_(n)Ge_(1-n) (where 0≦n≦1) is also preferablyperformed. Examples of such material include Al, Zn, Ag, Au, Sb, Sn, andIn. The term “addition” refers to a condition where the compositionalratio is lower than that of the compound between the element A andSi_(n)Ge_(1-n) (where 0≦n≦1), and compositions can be compared in unitsof atomic %.

In addition, one of the members of the structure of the presentinvention is occupied by the compound between the element A andSi_(n)Ge_(1-n) (where 0≦n≦1). However, the compound refers to thecondition where multiple bonds are present between Si_(n)Ge_(1-n) (where0≦n≦1) and the element A, and is not necessarily crystallized. Inparticular, an amorphous state is also preferable in terms ofapplication.

For example, a system composed of palladium and Si_(n)Ge_(1-n) (where0≦n≦1) has a eutectic phase diagram as shown in FIG. 4D between acompound comprised of Pd and Si_(n)Ge_(1-n) (where 0≦n≦1) (that is,A(SiGe)_(y), where A represents Pd; y will be described later) andSi_(n)Ge_(1-n) (where 0≦n≦1). In this case, the structure of the presentinvention can be formed. When the structure is present as a compoundbetween Pd and Si_(n)Ge_(1-n) (where 0≦n≦1), a separation structure maybe formed not only as the crystal of the compound but also as anamorphous substance.

Therefore, even when only Si_(n)Ge_(1-n) (where 0≦n≦1) is etched, acompound between Pd and Si_(n)Ge_(1-n) (where 0≦n≦1) in an amorphousstate may be etched owing to the presence of plural dangling bonds of Sior Ge even though a crystalline compound between Pd and Si_(n)Ge_(1-n)(where 0≦n≦1) is not etched. In this case, Si or Ge having a weak bondmay be etched, so one having a high Pd composition may remain. Asdescribed above, in the present invention, when one of the membersconstituting a structure is removed, the other member may be slightlycorroded.

The composition with respect to the element A that can be selected inthe present invention cannot be uniformly represented because thecompound between the element A and Si_(n)Ge_(1-n) (where 0≦n≦1) may takevarious states depending on materials. However, an element that can betaken to have a phase diagram shown in FIG. 4C or 4D out of such phasediagram as shown in FIG. 4B is effective. The value x of A_(x)(SiGe) inwhich the element A accounts for the majority as shown in FIG. 4C andthe value y of A(SiGe)_(y) in which Si_(n)Ge_(1-n) (where 0≦n≦1)accounts for the majority as shown in FIG. 4D are inherent for thematerial. However, the compositional range is determined once the valuesx and y are determined. For example, in the case of A_(x)(SiGe), thecomposition range [atomic %] of A with respect to the total amount of Aand Si_(n)Ge_(1-n) (where 0≦n≦1) is preferably selected from the rangeof (100x+10)/(x+1) to (100x+90)/(x+1) (both inclusive). It should benoted that the composition range shown here is the minimum requirementbecause whether the structure of the present invention is formed in thecomposition range depends on production conditions. Therefore, that itis the structure of the present invention is determined on the basis ofthe conditions that it falls within the composition range and that theabove-described ratio of the average diameter Dl in the major axisdirection to the average diameter Ds in the minor axis direction ofcolumnar members is less than 5. Furthermore, in the case ofA(SiGe)_(y), the composition range of A with respect to the total amountof A and Si_(n)Ge_(1-n) (where 0≦n≦1) is preferably selected from therange of 10y/(y+1) to 90y/(y+1) (both inclusive). The expression“A_(x)(SiGe)” represents the composition ratio at which X A's arepresent per one Si_(n)Ge_(1-n) (where 0≦n≦1) The same holds true forA(SiGe)_(y). For example, supposing the above-described system composedof a compound comprised of Pd and Si_(n)Ge_(1-n) (where 0≦n≦1) andSi_(n)Ge_(1-n) (where 0≦n≦1), the compound between Pd and Si_(n)Ge_(1-n)(where 0≦n≦1) is of the A(SiGe)_(y) type (where y=1). In other words,the compound is formed when A and Si_(n)Ge_(1-n) (where 0≦n≦1) are usedat an amount ratio of 1:1. The composition range of A at this time ispreferably selected from the range of 10y/(y+1) to 90y/(y+1) (bothinclusive), that is, from the range of 5 atomic % to 45 atomic % (bothinclusive) obtained by substituting y=1 into the preceding expression.This is valid also for the case where y=1 for the compound systembetween Pd and Si_(n)Ge_(1-n) (where 0≦n≦1). For example, if y=2, therange is from 6.667 atomic % to 60 atomic % (both inclusive).

Si_(n)Ge_(1-n) (where 0≦n≦1) described above represents the compositionof Si and Ge. Si composition is represented by 100n [atomic %] while Gecomposition is represented by 100(1-n) [atomic %]. On the other hand,A_(x)(SiGe) represents only the ratio between A and Si_(n)Ge_(1-n)(where 0≦n≦1). When the ratio is represented in terms of composition, Acomposition is represented by 100x(x+1) [atomic %], and Si_(n)Ge_(1-n)(where 0≦n≦1) composition is represented by 100(x+1) [atomic %].

The conditions under which the structure of the present invention isformed are not uniform, and are inherent for a material to be selected.The inventors of the present invention have made extensive studies tofind a certain correlation. Table 1 and Table 2 below each show thecorrelation. TABLE 1 Average diameter of Eutectic temperature columnarmembers Material [° C.] [nm] Cu₃Si—Si 800 7 PdSi—Si 860 5 NiSi—Si 9802.5 CoSi₂—Si 1258 2 TiSi₂—Si 1330 0 WSi₂—Si 1400 0

TABLE 2 Average diameter of Eutectic temperature columnar membersMaterial [° C.] [nm] Cu₃Ge—Ge 642 7 PdGe—Ge 728 4.5 NiGe—Ge 762 3.5TiGe₂—Ge 900 0

Table 1 and Table 2 above show the eutectic temperatures [° C.] ofseveral main materials selected in phase diagrams. The temperature ofthe substrate 104 is set to room temperature, and the average diameter[nm] of the columnar members of a structure produced by means of asputtering method without, for example, any application of a biasvoltage to the substrate 104 is shown together. The other conditions areas follows: argon having a pressure of 0.1 Pa is used as a process gas,and electric power to be input to a 4-inch-size target is 120 W for a Sisystem or 60 W for a Ge system. Attention is paid for establishing asituation where the composition is such that the upper end face of acolumnar member is substantially of a circular shape. Therefore, theaverage diameter is shown without distinguishing the major and minoraxis directions. In addition, the eutectic temperature is shown withreference to the general equilibrium diagram of bulk. In this case,however, some degree of error in the eutectic temperature hassubstantially no influence on the correlation found by the inventors ofthe present invention.

As can be seen from Table 1 and Table 2, the average diameter ofcolumnar members reduces with increasing eutectic temperatures, and thestructure of the present invention is not formed at a certaintemperature. The correlation between the eutectic temperature and theaverage diameter of columnar members may be formulated roughly (to afirst approximation) on the basis of four sets of data to form thestructure of the present invention out of the above result. Irrespectiveof material selected, what eutectic temperature of a material can beselected for a desired average diameter of columnar members can beunderstood. For a Si system, the following expression [1] is valid.[Eutectic temperature ° C.]=1,280° C.−75×[Average diameter (nm) ofcolumnar members]  [1]For a Ge system, the following expression [2] is valid.[Eutectic temperature ° C.]=897° C.−37×[Average diameter (nm) ofcolumnar members] [2]

Attention should be paid to the implication of the expressions [1] and[2] that a structure cannot be formed with a system in which the averagediameter of columnar members is 0, in other words, with a Si systemhaving a eutectic temperature of about 1,280° C. or higher, or a Gesystem having a eutectic temperature of about 897° C. or higher.However, this is because the conditions under which a structure isformed are fixed as described above. 1,280° C. in the case of a Sisystem or 897° C. in the case of a Ge system in the above correlation isadditionally increased by additionally increasing the temperature of thesubstrate 104 or by promoting the diffusion of elements on the substratesurface 503 through, for example, the application of a bias voltage tothe substrate 104. The examples shown here are for each of a Si systemand a Ge system; likewise, a SiGe system shows a similar tendency.

The expression [1] showing a correlation in a Si system and theexpression [2] showing a correlation in a Ge system differ largely fromeach other. This is attributable to the circumstance that the depositionrate of the Ge system is high because the sputtering yield of Ge (theprobability of causing Ge to sputter with respect to one process gas [anAr gas in this case]) is much higher than that of Si. When thedeposition rates of both systems are set to be equal to each other, thecorrelation in the Si system, the correlation in the Ge system, and acorrelation in a SiGe system can be represented by means of one formulawithout any discrimination. In the above sputtering, input power (RFpower) for the Si system is set to 120 W and the power for the Ge systemis set to 60 W so that the deposition rates of both systems come closerto each other. Even in this case, however, the deposition rate of the Gesystem is still higher than that of the Si system.

Description will be given of a PdSi system as a reference. The averagediameter of the columnar members of a structure to be formed can bechanged with a substrate temperature as shown in Table 3 below. TABLE 3Average diameter of Substrate temperature columnar members Material [°C.] [nm] PdSi—Si 25 5 200 6 300 7.2

In this case, the correlation represented by the following expression[3] can be obtained.[Substrate temperature ° C.]=575+124×[Average diameter (nm) of columnarmembers]  [3]

As described above, a structure having a columnar member having adesired size in a nano-scale region can be formed by finding a unifiedcorrelation not only for a specific material.

Therefore, the present invention provides a nano-scale structure havingan extremely effective phase-separated structure and a method ofproducing the same on the basis of the finding that a structure having aphase-separated structure formed therein can be formed even wheninvolving the formation of the compound, and of the finding of thecorrelation nearly irrespective of materials.

In addition, selecting appropriate composition for the structure of thepresent invention can bring the above-described ratio between averagediameters limitlessly closer to 1 and can reduce fluctuations indiameters of plural columnar members. This is because a eutectic phasediagram is obtained over a wide temperature range in an equilibriumdiagram as shown in FIG. 4, in other words, because separation occurs atonly one eutectic temperature present in a process for forming aphase-separated structure. Therefore, it can be easily assumed thatphase separation is repeated several times in a phase diagram whereplural phase separations are present, thereby resulting in a complexstructure.

[Porous Structure, Needle-Like Structure, and Methods of Producing theSame]

The porous structure, needle-like structure, and methods of producingthe same of the present invention will be described.

As shown in FIGS. 6A (a plan view) and 6B (a sectional view taken alongthe line 6B-6B of FIG. 6A), a porous structure that can be formed byremoving only columnar member portions from the structure of the presentinvention having the above phase-separated structure is composed ofplural fine pores 600 and a matrix portion 601 composed of a firstmember or second member. The fine pores 600 are characterized in thatthey extend substantially perpendicularly with respect to the substrate104, and that they are excellent in linearity. In addition, as shown inFIGS. 7A (a plan view) and 7B (a sectional view taken along the line7B-7B of FIG. 7A), a needle-like structure that can be formed byremoving a portion except columnar members from the structure of thepresent invention having the above phase-separated structure is composedof plural needle-like portions 601 composed of the first member orsecond member and a void portion 701 between the needle-like portions.The needle-like portions are characterized in that they extendsubstantially perpendicularly with respect to the substrate 104, andthat they are excellent in linearity.

An etching method with selectivity such as chemical wet etching, vaporphase etching, or plasma assist etching can be used as a method ofremoving only columnar member portions or a portion except columnarmembers upon production of the above porous structure or needle-likestructure. The structure of the present invention having the abovephase-separated structure, the structure serving as a starting point, isconstituted by a portion composed of a compound between the element Aand Si_(n)Ge_(1-n) (where 0≦n≦1) and a portion composed ofSi_(n)Ge_(1-n) (where 0≦n≦1). In such case, the chemical etching enablesonly Si_(n)Ge_(1-n) (where 0≦n≦1) to be etched by means of an etchingsolution such as an aqueous solution of KOH in a heated state. Inaddition, the use of an etching gas such as XeF₂ with which only Si canbe etched is effective for the vapor phase etching in the case whereSi_(n)Ge_(1-n) (where 0≦n≦1) has a low Ge composition or is free of Ge.In particular, etching with XeF₂ allows etching at a high aspect ratiomaking use of its high selectivity in spite of the fact that thediameter of each of the columnar members of the structure of the presentinvention, or an interval between columnar members is of a nanometersize. Furthermore, no assist with plasma or the like is needed, aportion except a portion to be etched is damaged little, and a resist orthe like receives no damage. Therefore, a process based on thecombination of self-organization film and photolithography can besmoothly performed. In the case where Si_(n)Ge_(1-n) (where 0≦n≦1) has ahigh Ge composition, it is also preferable to etch Ge or SiGe by meansof hydrogen peroxide. Alternatively, the structure of the presentinvention having the above phase-separated structure and serving as astarting point may be constituted by a portion composed of a compoundbetween the element A and Si_(n)Ge_(1-n) (where 0≦n≦1) and a portioncomposed of the element A. In such case, particularly when the element Ais a metal, the chemical etching is extremely effective in considerationof the high chemical resistance of the compound between the element Aand Si_(n)Ge_(1-n) (where 0≦n≦1). In particular, when the element A isreadily soluble in an acid or an alkali, the porous structure orneedle-like structure of the present invention can be quickly obtained.When electricity can be caused to flow into the structure, part of thestructure can be dissolved acceleratedly by arranging the structure onan anode side in an acid aqueous solution and applying a voltage.Finally, a portion except a portion to be etched may be subjected tooxidation due to, for example, the adsorption of oxygen to its surfacein the process for obtaining each of those porous structure andneedle-like structure. In particular, the application of a voltage is apreferable means for active oxidation because the application promotesoxidation.

Constituent elements of which the porous structure or needle-likestructure of the present invention is formed preferably include Li, Na,Mg, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Rb, Sr, Y, Zr, Nb, Mo, Ru,Rh, Pd, Cs, Ba, La, Hf, Ta, W, Re, Os, Ir, Pt, Ce, Pr, Nd, Sm, Gd, Tb,Dy, Ho, Er, Tm, Yb, Lu, or B. Furthermore, the constituent elements ofwhich the porous structure or needle-like structure is formed mayinclude Al, Zn, Ag, Au, Sb, Sn, In, or the like which is applicable asthe above-described additional element; provided that each of theseadditional elements is preferably added in a range in which the elementforms a solid solution with any one of the above constituent elements.

[Electronic Device Utilizing the Present Invention]

The term “electronic device” as used herein refers to, for example, aquantum dot, a quantum wire, a quantum wire transistor, a singleelectronic transistor, or a single electronic memory. The term alsoincludes an information processing system using any such device.

In particular, the structure of the present invention is composed of acompound between the element A and Si_(n)Ge_(1-n) (where 0≦n≦1) andSi_(n)Ge_(1-n) (where 0≦n≦1) or the element A.

Therefore, columnar members can be formed of a material called anenvironmental semiconductor such as a compound between Fe, Ca, Sr, Mg,Ba, or the like and Si_(n)Ge_(1-n) (where 0≦n≦1). Adding a trace elementto the columnar members to control conductivity can result in awire-like electronic device. Such cases include the case where light isemitted in accordance with each band gap. In addition, a transistorshown in FIG. 14 is permitted for what is called a quantum dot or aquantum wire. In other words, a structure 1401 of the present inventioncan be made into a transistor which has a source electrode 1403 and adrain electrode 1404 and which controls the movement of an electron bymeans of a gate electrode 1402. In addition, as described below, it isalso preferable to produce an electronic device by forming an electrodeportion on the structure of the present invention as shown in FIG. 15.

[Gate Electrode Utilizing the Present Invention]

As shown on the upper side of FIG. 15, a conventional transistor isconstituted by a source electrode 1501, a drain electrode 1502, a gateoxide film 1505, a spacer 1504, a gate electrode portion 1503, and asilicide 1506. In contrast, as shown on the lower side of FIG. 15, whenthe portion that has been conventionally the silicide 1506 is replacedwith a structure portion 1507 of the present invention, the gateelectrode portion 1503 of the present invention causes the anisotropy ofa material due to a columnar structure of the structure to reduce leakcurrent. As a result, a transistor or, finally, an integrated circuithaving small power consumption can be produced. The columnar member isconstituted by, for example, a compound between Ti, Co, Mo, or V andSi_(n)Ge_(1-n) (where 0≦n≦1) because the compound is excellent inelectric conductivity. The present invention includes an integratedcircuit using the gate electrode and an information processing systemmounted with the integrated circuit as well.

[Magnetic Recording Medium, Magnetic Recording/Reproducing Device, andInformation Processing System Each Utilizing the Present Invention]

The layer constitution of a magnetic recording medium for explaining amagnetic recording medium of the present invention will be describedwith reference to FIG. 8. The magnetic recording medium has a softmagnetic layer 801 formed on the substrate 104 in such a manner that amagnetic flux from a magnetic head converges on a recording layer 803;an underlayer 802 intended for controlling, for example, the structureof the recording layer or the orientation of a crystal; and therecording layer 803 formed through the layer 802. A protective layer 804and a lubricant layer 805 are preferably formed sequentially for theprevention of the deterioration of the medium, and floating stabilityand impact resistance of the head. It should be noted that this layerconstitution is a minimum requirement, and one or more layers may beappropriately inserted between two adjacent layers.

A first invention in the magnetic recording medium of the presentinvention is characterized in that there is provided a structure inwhich magnetic particles of the recording layer 803 are connected to therespective columnar members dispersed in a self-organization manner intothe structure of the present invention as the underlayer 802. Thisstructure will be explained with reference to FIGS. 9A (a plan view) and9B (a sectional view taken along the line 9B-9B of FIG. 9A). Thisstructure is characterized in that a layer (film) composed of thestructure of the present invention is applied as the underlayer 802, andhard magnetic particles 901 in the recording layer 803 are continuouslyconnected to the respective columnar members of the structure. Themagnetic recording medium is characterized in that a region except thecolumnar member portions of a layer 900 composed of the structure of thepresent invention is continuously connected to a non-magnetic region 902in the recording layer 803. The present invention is characterized inthat, the nucleus formation of the hard magnetic particles 901 can becaused quickly by the columnar members of the underlayer at an initialstage of the formation of the recording layer 803 containing the hardmagnetic particles 901.

The constituent element A of the structure of the present invention ofwhich the underlayer is formed preferably contains Li, Na, Mg, K, Ca,Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Rb, Sr, Y, Zr, Nb, Mo, Ru, Rh, Pd,Cs, Ba, La, Hf, Ta, W, Re, Os, Ir, Pt, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho,Er, Tm, Yb, Lu, or B. Furthermore, a chemical vapor deposition method, asputtering method, an evaporation method, a plating method, or the likeis a preferable method of forming the recording layer 803. A depositionmethod in a vapor phase such as the sputtering method is particularlypreferable.

A CoCr, CoCrPt, CoCrPtB, CoCrPtTa, CoPt—MgO, FePt—MgO, CoPt—SiO₂,FePt—SiO₂, CoCrPt—SiO₂, Co/Pt-based, Fe/Pt-based, Co/Pd-based, orFe/Pd-based multilayer film or the like having appropriate compositionsis preferably selected as a material for the recording layer 803.

Any other material is applicable as long as a deposition method in avapor phase such as a sputtering method is applicable to the material.In addition, the columnar members of the structure of the presentinvention are preferably arranged in a honeycomb fashion in aself-organization manner on the surface of the underlayer 802. As aresult, variances of the particle sizes of the hard magnetic particles901 having an average diameter of 20 nm or less can be reduced. As aresult, a magnetic recording medium with an extremely low-noise can beprovided. This is attributable to the effectiveness of thecharacteristic that the variance of the average diameter of the columnarmembers in the structure of the present invention is extremely small.The term “honeycomb arrangement” as used herein refers to an arrangementin a certain region, and permits arrangement disorder between differentregions.

Next, a second invention of the magnetic recording medium of the presentinvention is a magnetic recording medium having a recording layerobtained by removing only columnar member portions of the structure ofthe present invention and filling the resultant with a hard magneticmaterial. This case is similar to the case where the fine pores of theporous structure of the present invention are filled with a hardmagnetic material. FIGS. 10A (a plan view) and 10B (a sectional viewtaken along the line 10B-10B of FIG. 10A) each show the second inventionof the magnetic recording medium, and are a schematic view of therecording layer 803. This magnetic recording medium is characterized inthat its hard magnetic material has the same shape as that of each ofthe columnar members of the structure of the present invention. This isbecause the fine pores 600 of the porous structure obtained by removingonly the columnar members from the structure are filled with a hardmagnetic material. Therefore, the columnar members are each preferablycomposed of a hard magnetic material 1000, and a portion except them ispreferably a non-magnetic region 1001 composed of a first member or asecond member. The first member or the second member refers to theabove-described member in the structure of the present invention. Themembers are respectively a member containing a compound between theelement A and Si_(n)Ge_(1-n) (where 0≦n≦1) and a member containingSi_(n)Ge_(1-n) (where 0≦n≦1) or the element A.

The element A is preferably selected from Li, Na, Mg, K, Ca, Sc, Ti, V,Cr, Mn, Fe, Co, Ni, Cu, Rb, Sr, Y, Zr, Nb, Mo, Ru, Rh, Pd, Cs, Ba, La,Hf, Ta, W, Re, Os, Ir, Pt, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb,Lu, and B. Although some of those elements may have magnetism dependingon composition, none of them can have hard magnetism in a compoundbetween the element and Si_(n)Ge_(1-n) (where 0≦n≦1). Therefore, theelement can be used in a mode where a member except a columnar member isformed of at least a compound between the element and Si_(n)Ge_(1-n)(where 0≦n≦1).

In addition, the hard magnetic material 1000 is preferably selected froma material mainly composed of Co, Fe, MPt (M is composed of one or moreof Co, Fe, and Ni) as an L1₀ ordered alloy, or M₃Pt (M is composed ofone or more of Co, Fe, and Ni) as an L1₂ ordered alloy; a multilayerfilm mainly composed of Co or Fe and Pt or Pd; and the like. The finepores 600 of the porous structure may be filled with the hard magneticmaterial by means of any method as long as the material is introducedinto the fine pores; provided that a chemical vapor deposition method, asputtering method, a evaporation method, a plating method, or the likeis preferable. When an electroplating method is adopted, the underlayer802 below the recording layer 803 preferably contains a low-resistancemetal.

Furthermore, a third invention of the magnetic recording medium of thepresent invention is a magnetic recording medium having a soft magneticlayer obtained by removing only columnar member portions of thestructure of the present invention and filling the resultant with a softmagnetic material. This case is similar to the case where the fine poresof the porous structure of the present invention are filled with a softmagnetic material. FIGS. 11A (a plan view) and 11B (a sectional viewtaken along the line 11B-11B of FIG. 11A) each show the third inventionof the magnetic recording medium, and are a schematic view of the softmagnetic layer 801. This magnetic recording medium is characterized inthat its soft magnetic material has the same as that of each of thecolumnar members of the structure of the present invention. This isbecause the fine pores 600 of the porous structure obtained by removingonly the columnar members from the structure are filled with a softmagnetic material. Therefore, the columnar members are each preferablycomposed of a soft magnetic material 1100, and a portion except them ispreferably a non-magnetic region 1001 composed of a first member or asecond member. The first member or the second member refers to theabove-described member in the structure of the present invention. Themembers are respectively a member containing a compound between theelement A and Si_(n)Ge_(1-n) (where 0≦n≦1) and a member containingSi_(n)Ge_(1-n) (where 0≦n≦1) or the element A. The element A ispreferably selected from Li, Na, Mg, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co,Ni, Cu, Rb, Sr, Y, Zr, Nb, Mo, Ru, Rh, Pd, Cs, Ba, La, Hf, Ta, W, Re,Os, Ir, Pt, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and B. Thesoft magnetic material 1100 is preferably selected from an alloy havinga high magnetic permeability composed of two or more of Co, Fe, and Ni;or mainly composed of M₃Pt (M is composed of one or more of Co, Fe, andNi) as an L1₂ ordered alloy or the like. Although the fine pores 600 ofthe porous structure may be filled with the soft magnetic material bymeans of any method as long as the material is introduced into the finepores, a chemical vapor deposition method, a sputtering method, anevaporation method, a plating method, or the like is preferable. When anelectroplating method is adopted, the substrate 104 below the softmagnetic layer 801 preferably contains a low-resistance metal.

Furthermore, a magnetic recording/reproducing device of the presentinvention is characterized by using the above-described first, second,and third inventions of the magnetic recording medium of the presentinvention. As shown in a schematic view shown in FIG. 12, the magneticrecording/reproducing device is constituted by, in a casing, anymagnetic recording medium 1200 of the present invention, a magneticrecording medium driving portion 1201 driving the medium, a magnetichead 1202, a magnetic head driving portion 1203, and a signal processingportion 1204. The recording/reproducing mode of the magneticrecording/reproducing device of the present invention is not limited tothe rotation of the medium and the driving of the head on an arc asshown in FIG. 12.

An information processing system using the magneticrecording/reproducing device of the present invention will be described.As shown in FIG. 13, the information processing system of the presentinvention houses, in a housing container 1300, a magneticrecording/reproducing device 1301, an operating portion 1302, a memoryportion 1303, and a power source 1304. The information processing systemis characterized in that the respective components are connected to oneanother by means of wiring 1306, and various pieces of information areexchanged through an external input/output portion 1305. In addition,each of the wiring 1306 and the external input/output portion 1305 doesnot refer to only a wired one, and it is also preferable that each ofthem be wireless as long as information can be transferred.

[Functional Film Having Catalytic Ability Using Porous Structure andNeedle-Like Structure of the Present Invention]

Each of the above-described porous structure and needle-like structureof the present invention has a considerably increased surface area ascompared to that of an ordinary film state. In addition, a nano-scalestructure is repeated. Therefore, the above-described porous structureand needle-like structure is characterized in that they have many meritsbecause of its nano-scale size unlike a similar structure of a micronsize. The same shape of the porous structure of the present invention isrealized by means of columnar members having an average diameter of 1 μmwith an average interval between centers of gravity of columnar membersof 1.3 μm. This shape is compared with an example of the porousstructure of the present invention including columnar members having anaverage diameter of 6 nm with an average interval between centers ofgravity of columnar members of 8 nm. The area ratio between side facesof columnar members corresponds to a difference in surface area betweenthe two structures to be compared. When an approximation to assume thata columnar member is of a circular shape is performed, the area of theside face of each columnar member is represented by πRh (where Rrepresents a diameter and h represents a height). When the number ofcolumnar members per unit area is n, the surface area per unit area canbe represented by πRhn. Therefore, the structures are different in R andn because they are compared with their film thicknesses set to be equalto each other. As a result, the ratio between their R's is 6 [nm]/1,000[nm], and the ratio between their n's is about 3.0×10¹⁰[members]/1.2×10⁶ [members] (calculated in terms of 1.3-mm square).Therefore, the product of the ratio between R's and the ratio betweenn's is 150. This means that the structure of the present invention canhave a surface area 150 times as large as that of the micron-scalestructure. In view of the foregoing, the structure of the presentinvention is found to be extremely effective for an approach toeffectively utilize surface area, that is, a functional film havingcatalytic ability. In addition, in a functional film of the presentinvention, the first member or second member 601 in the porous structureor the first member or second member 601 in the needle-like structurepreferably contains a noble metal material having catalytic ability. Inparticular, such member preferably contains Pd or Pt, or more preferablycontains an alloy system of such metal and any other material forreducing the amount of a noble metal to be used. A noble metal exertingdesired catalytic ability can be appropriately selected and used.Therefore, in the present invention, a porous structure or needle-likestructure composed of Pd or Pt can be formed. Alternatively, a structuremainly composed of PdSi, PtSi, PdGe, PtGe, or the like is alsopreferable. In this case, the composition range of Pd or Pt with respectto the entire film (porous structure or needle-like structure) is around50%, so the surface area is increased owing to the nano-scale, and theamount of a noble metal to be used can be reduced in half. Such catalystcan be used for the efficient generation of hydrogen in a fuel cell orthe like. Each of the porous structure and the needle-like structure isparticularly preferably integrated with a polymer electrolyte filmresponsible for proton conductivity. In other words, a constitutionshown in each of FIGS. 16 and 17 as schematic views is preferable. In aporous structure, part of an electrolyte film 1601 preferably penetratesalong the walls of the fine pores 600 of a noble-metal-containingmembrane 1603 to become integrated. In addition, in a needle-likestructure, noble-metal-containing rods 1700 are preferably surrounded bypart of the electrolyte film 1601 for integration. Such structure can beproduced by producing the porous structure or the needle-like structure,applying and pressure-bonding the electrolyte film, and peeling off theresultant from the substrate 104 supporting a structure portion. Thefine pores 600 or the noble metal-containing rods 1700 are not needed tobe arranged in a complete honeycomb fashion as shown in the figures, andhave to be only arranged uniformly.

[Electron Emitting Device Using Structure and Needle-Like Structure ofthe Present Invention]

An electron emitting device of the present invention is obtained byproviding the structure of the present invention with a lead-outelectrode. Since the structure of the present invention has a nano-scalephase-separated structure, an electric field concentrates on eachcolumnar member having a low resistance, so an electron emitting devicehaving a reduced threshold can be formed. Preferably, an electronemitting device in which a side face as well as the outermost surfaceare involved can be formed by removing a portion except the columnarmembers in the structure of the present invention.

As shown in schematic views of FIG. 18, a lead-out electrode 1803 havingan opening including plural columnar members to serve as electronemitting portions 1801 is formed so as to be apart from the electronemitting portions 1801 by an insulation layer 1802. A voltage is appliedby a bias applying circuit 1805 between an underelectrode 1800 placedbelow the electron emitting portions 1801 and the lead-out electrode1803. As a result, electrons drawn from the electron emitting portions1801 are emitted in an electron emission direction.

One shown in schematic views of FIG. 19 is also available depending onthe insulating property of a material between columnar members in thepresent invention. In other words, the void portion 701 is preferablyformed by removing only part of the first member or second member 601except a columnar member portion, the part corresponding to the openingprovided for the lead-out electrode 1803. In this case, when a voltageis applied by the bias applying circuit 1805 between the electronemitting portions 1801 and the lead-out electrode 1803 via theunderelectrode 1800, electrons are emitted in the electron emissiondirection. Therefore, an electron emitting device having high electronemission efficiency can be formed.

The mode of the electron emitting device is not limited to those shownin FIGS. 18 and 19. In particular, a structure in which a bias isapplied to the space between columnar members which is one phase of thestructure of the present invention to emit an electron is alsopreferable. An electron emitting device similar to this can be obtainedalso by means of the needle-like structure of the present inventionhaving the void portion 701. Furthermore, it is also preferable to coatthe surface of each of the electron emitting portions 1801 in the aboveelectron emitting device with a thin layer of carbon.

The above-described invention of an electron emitting device includes animage display device obtained by arranging a large number of suchdevices.

EXAMPLE 1

This example relates to the formation of the structure of the presentinvention.

A structure belonging to the scope of the present invention is composedof a binary system mainly composed of Si_(n)Ge_(1-n) (where 0≦n≦1) andan element A, and may contain further components. In this example, aPdSi—Si system, a PdGe—Ge system, and a PdSiGe—SiGe system will betaken, and their structures will be described.

At first, as shown in FIG. 20, one 12-mm square Pd metal piece isarranged at a center on a Si sputtering target, and a Ge substrate isselected as the substrate 104. The distance between the target and thesubstrate is about 80 mm, and the substrate is arranged directly abovethe target. Film formation is performed for 5 minutes under thefollowing deposition conditions: the temperature of the substrate isroom temperature, no DC bias is applied to the substrate, input electricpower is RF 120 W, and an argon gas pressure is 0.1 Pa.

Similarly, two 12-mm square Pd metal pieces are arranged at a center ona Ge sputtering target, and a Si substrate is selected as the substrate104. The distance between the target and the substrate is about 80 mm,and the substrate is arranged directly above the target. Film formationis performed for 5 minutes under the following deposition conditions:the temperature of the substrate is room temperature, no DC bias isapplied to the substrate, input electric power is RF 60 W, and an argongas pressure is 0.1 Pa.

Then, the surface structures and sectional structures of the filmsformed on those substrates are observed with a scanning electronmicroscope.

As a result, in the PdSi—Si system, a surface structure which is of acircular shape and which is composed of columnar PdSi portions having anaverage diameter of about 3 nm and a Si portion surrounding the PdSiportions is observed on the Ge substrate. Furthermore, the sectionalobservation confirms that the PdSi portions have columnar structuresextending perpendicularly from a substrate surface in the direction inwhich the film is deposited. The analysis of the composition of each ofSi and Pd with X-ray fluorescence measurements shows that Pd accountsfor about 12 atomic % in this case. In addition, the film thickness isabout 40 nm.

In the PdGe—Ge system, a surface structure which is of a circular shapeand which is composed of columnar PdGe portions having an averagediameter of about 4.5 nm and a Ge portion surrounding the PdGe portionsis observed on the Si substrate. Furthermore, the sectional observationconfirms that the PdGe portions have columnar structures extendingperpendicularly from a substrate surface in the direction in which thefilm is deposited. The analysis of the composition of each of Ge and Pdwith X-ray fluorescence measurements shows that Pd accounts for about 15atomic % in this case. In addition, the film thickness is about 50 nm.

Film formation is performed on the PdSi—Si system under the samedeposition conditions by arranging three 12-mm square Pd metal pieces onthe Si sputtering target. The film thus obtained has a surface structurewhich is of a circular shape and which is composed of columnar Siportions having an average diameter of about 3 nm and a PdSi portionsurrounding the Si portions. Furthermore, the sectional observationconfirms that the Si portions have columnar structures extendingperpendicularly from a substrate surface in the direction in which thefilm is deposited. The analysis of the composition of each of Si and Pdwith X-ray fluorescence measurements shows that Pd accounts for about 37atomic % in this case. In addition, the film thickness is about 45 nm.

Film formation is performed on the PdGe—Ge system under the samedeposition conditions by arranging four 12-mm square Pd metal pieces onthe Ge sputtering target. The film thus obtained has a surface structurewhich is of a circular shape and which is composed of columnar Geportions having an average diameter of about 4.5 nm and a PdGe portionsurrounding the Ge portions. Furthermore, the sectional observationconfirms that the Ge portions have columnar structures extendingperpendicularly from a substrate surface in the direction in which thefilm is deposited. The analysis of the composition of each of Ge and Pdwith X-ray fluorescence measurements shows that Pd accounts for about 35atomic % in this case. In addition, the film thickness is about 50 nm.

Furthermore, film formation is performed by arranging one 12-mm squarePd metal piece and one 10-mm square Ge metal piece on the Si sputteringtarget at an input electric power of RF 100 W. A MgO substrate is usedas a substrate. The film thus obtained has a surface structure which isof a circular shape and which is composed of columnar PdSiGe portionshaving an average diameter of about a little under 3 nm and a SiGeportion surrounding the PdSiGe portions. Furthermore, the sectionalobservation confirms that the PdSiGe portions have columnar structuresextending perpendicularly from a substrate surface in the direction inwhich the film is deposited. The analysis of the composition of each ofSiGe and Pd with X-ray fluorescence measurements shows that Pd accountsfor about 10 atomic % in this case. In addition, the film thickness isabout 45 nm. As described above, the formation of the structure of thepresent invention is confirmed even in the PdSiGe—SiGe system as in thecase of each of the PdSi—Si system and the PdGe—Ge system.

Film formation is performed by arranging three 12-mm square Pd metalpieces and one 10-mm square Ge metal piece on the Si sputtering targetat an input electric power of RF 100 W. An MgO substrate is used as asubstrate. The film thus obtained has a surface structure which is of acircular shape and which is composed of columnar SiGe portions having anaverage diameter of about a little under 3 nm and an PdSiGe portionsurrounding the SiGe portions. Furthermore, the sectional observationconfirms that the SiGe portions have columnar structures extendingperpendicularly from a substrate surface in the direction in which thefilm is deposited. The analysis of the composition of each of SiGe andPd with X-ray fluorescence measurements shows that Pd accounts for about39 atomic % in this case. In addition, the film thickness is about 50nm. As described above, the formation of the structure of the presentinvention is confirmed even in the PdSiGe—SiGe system as in the case ofeach of the PdSi—Si system and the PdGe—Ge system.

The foregoing description shows the following. As shown in FIG. 1 asschematic views each showing the structure of the present invention, achange in composition can achieve either one of the first combination103 in which the compound (PdSi, PdGe, or PdSiGe in this example)between the element A and Si_(n)Ge_(1-n) (where 0≦n≦1) is columnarmembers, and Si_(n)Ge_(1-n) (where 0≦n≦1) (Si, Ge, or SiGe in thisexample) or the element A is a member surrounding the columnar members;and the second combination 102 in which the constituent elements of therespective members in the first combination 103 are replaced with eachother.

EXAMPLE 2

This example relates to means for determining whether a structure to beobtained is within the scope of the present invention.

Determination is performed in accordance with the flow chart shown inFIG. 2 by means of a scanning electron micrograph of the structuredescribed in Example 1 having PdSi columnar structures with an averagediameter of about 3 nm as one example.

It should be noted that an image obtained by binarizing the above imagecorresponds to an image shown on the left in (b) of FIG. 2. In addition,the average diameter Dl in the major axis direction and the averagediameter Ds in the minor axis direction are calculated from thebinarized image in accordance with (c-1). As a result, each of theaverage diameters Dl and Ds is found to be about 3 nm. Therefore, theratio Dl/Ds is calculated to be 1. Since the calculated value satisfiesthe condition that Dl/Ds is less than 5 as defined in the presentinvention, the structure is determined to be that of the presentinvention.

Furthermore, judgement in accordance with the flow chart shown in FIG. 2is performed again by using a structure obtained by arranging one 12-mmsquare Pd plate and two 6-mm square Pd plates near the center of the Sisputtering target unlike Example 1. In this case, an image shown on theright in (b) of FIG. 2 is the corresponding image. At first, the imageis binarized. As a result, it is soon found that the upper surfaces ofsome columnar members apparently have an elongated shape having a bentportion, so that one realizes it is not easy to calculate the averagediameter Dl in the major axis direction. Therefore, the area of theupper end face of each of the columnar members is divided by thecalculated value of the average diameter Ds in the minor axis directionof about 4 nm in accordance with the process of (c-2) in the chart. Theaverage of the values obtained through the division is calculated. Thus,the average diameter Dl in the major axis direction is about 9 nm. Theratio Dl/Ds is finally calculated to be 9/4, that is, 2.25. Therefore,it is shown that the resultant structure belongs to the structure of thepresent invention because the ratio is less than 5.

EXAMPLE 3

This example shows that the structure of the present invention can beselected from plural materials in which a correlation is found to showthe existence of the structure irrespective of the materials.

Film formation is attempted on a composition in which the upper end faceof a columnar member of a phase-separated structure is of a circularshape as in the case of Example 1 in each of a Cu₃Si—Si system, aPdSi—Si system, a NiSi—Si system, a CoSi₂—Si system, a TiSi₂—Si system,a WSi₂—Si system, a Cu₃Ge—Ge system, a PdGe—Ge system, a NiGe—Ge system,and a TiGe₂—Ge system. Observation with a scanning electron microscopereveals that the average diameter of those structures is as shown inTable 1 and Table 2 previously described, in which the composition ofthe PdSi—Si system here is different from that of Example 1.

Table 1 and Table 2 each list a eutectic temperature [° C.] read fromthe equilibrium diagram of bulk and the average diameter [mm] of thecolumnar members observed in this example. The correlation between thepreviously described expressions [1] and [2] can be found from thetemperature and the average diameter.

As described above, a meaningful relationship can be derived, whichindicates not largely depending on dissimilar materials or a differencein composition in deposition conditions or compositions with which asimilar structure can be obtained. This is an unexpected, new discovery,and is one of the most important items in the present invention.

EXAMPLE 4

This example relates to a correlation concerning the condition that thestructure size or the like of the structure of the present inventionvaries even in the same material and composition.

In this example, description will be given of a PdSi—Si system as arepresentative example. Film formation is performed under the sameconditions as those of Example 3 except that only the temperature of thesubstrate is changed to room temperature (25° C.), 200° C., and 300° C.Then, the average diameter of the upper end face of PdSi formingcolumnar members is measured. The result is as shown in Table 3. Thatis, the average diameter of the columnar members of a structure to beformed varies with the temperature of the substrate as shown in Table 3.The correlation represented by the above expression [3] can be foundfrom this result.

This correlation is also one of the most important items in the presentinvention. The correlation together with Example 3 can provide aguideline on what kind of material is preferably subjected to filmformation under what kind of conditions in order to obtain the desireddiameter of a columnar member.

EXAMPLE 5

This example relates not to a change in structure owing to the kind orcomposition of a raw material but to a change in structure with aparameter that can be controlled in a sputtering process.

At first, examples of a parameter in the sputtering method includedistance between a sputtering target and a substrate, input electricpower, kind and pressure of a process gas, temperature of the substrateand application of a substrate bias.

At first, electric power to be input to a 4-inch target is set to 120 W,and an argon gas pressure and the temperature of a substrate are fixedto 0.1 Pa and room temperature, respectively. A PdSi—Si system is usedas a representative example to observe a difference in structure amongdistances between the sputtering target and the substrate (each of whichmay hereinafter be referred to as the substrate distance) of 60 mm, 90mm, and 120 mm. A Ge substrate is used as the substrate. With increasingsubstrate distance, the boundary between columnar structures of PdSi isobserved to become slightly unclear and the size distribution isobserved to enlarge. Therefore, it can be confirmed that energy is lostduring the travel of the flying raw material particles caused to sputterto the substrate with increasing substrate distance.

Next, the distance between the sputtering target and the substrate isfixed to 90 mm, and a comparison between an input electric power of 200W and an input electric power of 120 W is performed. The columnarstructures of PdSi are observed to become slightly unclear, and theiraverage diameter is observed to reduce. Therefore, it can be confirmedthat phase separation due to the diffusion of elements on the substrateis inhibited by the fast deposition rate with an increase in depositionrate due to an increase in input electric power.

Furthermore, the distance between the sputtering target and thesubstrate and input electric power are fixed to 90 mm and 120 W,respectively, and a difference in structure between an argon gaspressure of 0.25 Pa and an argon gas pressure of 0.1 Pa is observed.With increasing argon gas pressure, the average diameter of PdSi havingcolumnar structures is observed to reduce, and a boundary between thecolumnar structures is observed to become slightly unclear. That is, itcan be confirmed that it is attributable to the loss of energy of rawmaterial particles during the flying of the particles with increasinggas pressure and the inhibition of diffusion on the substrate.

The substrate temperature is as shown in Example 4. It should be notedthat a substrate temperature near a eutectic temperature in theequilibrium diagram of bulk is not preferable because not diffusion on atwo-dimensional surface but three-dimensional diffusion as in bulk isdominant. However, it can be found that the description of Example 4 isapproximately valid up to a certain temperature.

Finally, the application of a substrate bias will be described.Substrate biases of DC 0 V, −20 V, and −40 V were applied with thedistance between the sputtering target and the substrate, input electricpower, argon gas pressure, and temperature of the substrate set to 90mm, 120 W, 0.1 Pa, and room temperature, respectively. It should benoted that a substrate having a low resistance is used because no DCbias can be applied when a substrate has a large resistance. Theapplication of an RF bias can cope with an insulating substrate. In thiscase, the average diameter, which is small when no bias is applied, ofthe columnar structures of PdSi is found to significantly increase withincreasing applied bias. For example, an effect of a substrate bias isas described below. An ionized particle is drawn into a substrate, andis caused to collide with a particle on the substrate, and the energy ofsurface diffusion increases as a result of energy transfer, therebyincreasing an average diameter. It is also found that when this effectis excessive, a phenomenon similar to that in the case of sputteringoccurs, so a particle on the surface of the substrate desorbs, therebyresulting in no formation of a film.

As can be seen from the foregoing, a structure can be controlled bychanging various parameters in the sputtering method.

EXAMPLE 6

This example relates to a porous structure obtained by removing onlycolumnar member portions from the structure having a phase-separatedstructure of the present invention.

Description will be given of the PdSi—Si system shown in Example 1 as arepresentative example. At first, a filmy structure obtained whenarranging three 12-mm square Pd plates near the center of a sputteringtarget and a filmy structure obtained by changing the temperature of asubstrate to 300° C. in the preceding circumstance are prepared. Thecolumnar members of the former filmy structure are composed of Si, andhave an average diameter of about 3 nm. On the other hand, the columnarmembers of the latter filmy structure are composed of Si, and have anaverage diameter of about 5 nm.

The porous structure of the present invention can be formed by removingthe Si portions of each of the filmy structures. An approach havingselectivity with which only Si can be etched is preferably adopted forthe removal of the Si portions. It is found that Si can be selectivelyetched through immersion in an aqueous solution of KOH at about 60° C.However, in the former case of this example, a PdSi portion surroundingSi in the form of columnar members is not sufficiently crystallized, andis of an amorphous state. Therefore, the PdSi portion is also found tobe slowly etched simultaneously with the etching of Si owing to thepresence of a dangling bond of Si. On the other hand, in the lattercase, the crystallization of the PdSi portion has progressed, so onlythe target Si columnar members are removed without the corrosion of thePdSi portion in the etching. As a result, a porous structure can beobtained. The etching, which has been performed in a liquid in theforegoing, can be preferably performed in a vapor phase as well. In viewof the foregoing, a method utilizing selective etching of Si in an XeF₂gas atmosphere can be attempted on each of the above two kinds of filmystructures. It is confirmed that the former filmy structure is notpreferably applicable to the formation of the porous structure of thepresent invention because not only the Si portions constituting thecolumnar members but also Si of the PdSi portion is removed. However, itcan be confirmed that, in the latter filmy structure, PdSi iscrystallized so sufficiently that only the Si columnar member portionsare selectively etched.

As can be seen from the foregoing, the structure having aphase-separated structure of the present invention is not limited to thecase where a compound portion between the element A and Si_(n)Ge_(1-n)(where 0≦n≦1) is sufficiently crystallized. The use of a structure inwhich the crystallization of a compound portion between the element Aand Si_(n)Ge_(1-n) (where 0≦n≦1) has progressed to some extent ispreferable for selective etching upon formation of the porous structureof the present invention.

In addition, this example is described with a structure composed of acompound comprised of the element A and Si_(n)Ge_(1-n) (where 0≦n≦1) andSi_(n)Ge_(1-n) (where 0≦n≦1) as a starting point. However, the sameholds true for a structure composed of the compound comprised of theelement A and Si_(n)Ge_(1-n) (where 0≦n≦1) and the element A. In otherwords, selective etching can be performed by utilizing high chemicalresistance, heat resistance, or the like of the compound between theelement A and Si_(n)Ge_(1-n) (where 0≦n≦1) the crystallization of whichhas progressed. Furthermore, when the element A is a metal, selectiveetching can be easily performed by means of, for example, an acid oralkali etching solution proper to the metal. In this case, the porousstructure of the present invention can be obtained even when thecompound portion between the element A and Si_(n)Ge_(1-n) (where 0≦n≦1)is not sufficiently crystallized because the metal is readily soluble inan acid although the solubility varies from metal to metal.

EXAMPLE 7

This example relates to a needle-like structure obtained by removing aportion except columnar member portions from the structure having aphase-separated structure of the present invention.

Description will be given of the PdSi—Si system shown in Example 1 as arepresentative example in accordance with the approach of Example 6. Atfirst, a filmy structure obtained by arranging one 12-mm square Pd platenear the center of a sputtering target and a filmy structure obtained bychanging the temperature of a substrate to 300° C. in the precedingcircumstance are prepared. The columnar members of the former filmystructure are composed of PdSi, and have an average diameter of about 3nm. On the other hand, the columnar members of the latter filmystructure are composed of PdSi, and have an average diameter of about 5nm. Of course, the portion except columnar portions is composed of Si.

The needle-like structure of the present invention can be formed byremoving the Si portions of each of the filmy structures. An approachhaving selectivity with which only Si can be etched is preferablyadopted for the removal of the Si portions. It is found that Si can beselectively etched through immersion in an aqueous solution of KOH atabout 60° C. However, in the former case of this example, a PdSi portionin the form of columnar members is not sufficiently crystallized, and isof an amorphous state. Therefore, the PdSi portion is also found to beslowly etched simultaneously with the etching of Si owing to thepresence of a dangling bond of Si. On the other hand, in the lattercase, the crystallization of the PdSi portion has progressed, so onlythe target Si composing a portion of except columnar members are removedwithout the corrosion of the PdSi portion in the etching. As a result, aneedle-like structure can be obtained. The etching, which has beenperformed in a liquid in the foregoing, can be preferably performed in avapor phase as well. In view of the foregoing, a method utilizingselective etching of Si in an XeF₂ gas atmosphere can be attempted oneach of the above two kinds of filmy structures. It is confirmed thatthe former filmy structure is not preferably applicable to the formationof the needle-like structure of the present invention because not onlythe Si portions constituting the portion except columnar members butalso Si of the PdSi portion constituting the columnar members isremoved. However, it can be confirmed that, in the latter filmystructure, PdSi is crystallized so sufficiently that only the Siconstituting the portion except columnar member portions are selectivelyetched.

As can be seen from the foregoing, the structure having aphase-separated structure of the present invention is not limited to thecase where a compound portion between the element A and Si_(n)Ge_(1-n)(where 0≦n≦1) is sufficiently crystallized. The use of a structure inwhich the crystallization of a compound portion between the element Aand Si_(n)Ge_(1-n) (where 0≦n≦1) has progressed to some extent ispreferable for selective etching upon formation of the needle-likestructure of the present invention.

In addition, this example has been described with a structure composedof a compound between the element A and Si_(n)Ge_(1-n) (where 0≦n≦1);and Si_(n)Ge_(1-n) (where 0≦n≦1) as a starting point. However, the sameholds true for a structure composed of the compound between the elementA and Si_(n)Ge_(1-n) (where 0≦n≦1) and the element A. In other words,selective etching can be performed by utilizing high chemicalresistance, heat resistance, or the like of the compound between theelement A and Si_(n)Ge_(1-n) (where 0≦n≦1) the crystallization of whichhas progressed. Furthermore, when the element A is a metal, selectiveetching can be easily performed by means of, for example, an acid oralkali etching solution proper to the metal. In this case, theneedle-like structure of the present invention can be obtained even whenthe compound portion between the element A and Si_(n)Ge_(1-n) (where0≦n≦1) is not sufficiently crystallized because the metal is readilysoluble in an acid although the solubility varies from metal to metal.

EXAMPLE 8

This example relates to an electronic device using the structure havinga phase-separated structure of the present invention.

Three electrodes are arranged on an upper portion of the structure 1401of the present invention. When the electrodes are arranged just as shownin FIG. 14, one substantially columnar member is arranged among theelectrodes. This situation can be realized by using, as a representativeexample, the structure of the present invention composed of NiSicolumnar members each composed of a NiSi—Si system and Si surroundingthe members. A tunnel current between left and right electrodes (thesource electrode 1403 and the drain electrode 1404) shown in FIG. 14 ismeasured. When a bias is applied at a lower electrode (the gateelectrode 1402) shown in FIG. 14, no tunnel current is observed.However, the cancellation of the bias enables a tunnel current to beobserved. As a result, it can be confirmed that electrons passed betweenelectrodes while tunneling through a Si region between NiSi columnarmembers. Therefore, the use of the structure of the present invention isfound to be effective for an electronic device or single electronicdevice such as a quantum dot or a quantum wire.

EXAMPLE 9

This example relates to a gate electrode using the structure having aphase-separated structure of the present invention.

A filmy structure 1507 of the present invention having columnar memberseach composed of TiSi₂, CoSi₂, or the like and Si surrounding themembers will be taken as a representative example. Film formation isconducted on a gate electrode portion 1503 shown in FIG. 15B is formed(the formation is applicable to each of the source electrode portion1501 and the drain electrode portion 1502). In a comparative example, ametal film composed of Ti, Co, or the like is similarly deposited, andis diffused through quick heating to form, at an interface, the gateelectrode portion 1503 composed of the silicide 1506 such as TiSi₂ orCoSi₂ (the formation is applicable to each of the source electrodeportion 1501 and the drain electrode portion 1502). In FIGS. 15A and15B, reference numeral 1504 denotes a spacer, and reference numeral 1505denotes a gate oxide film. The leak current values of transistors usingthose electrodes are compared. As a result, it can be confirmed that,when the structure of the present invention is used, a columnar memberportion guides a current only to a vertical direction so that leak in anin-plane direction is suppressed. Therefore, it is found to be effectiveto provide the gate electrode of the present invention with anisotropyin the direction in which a current is caused to flow.

EXAMPLE 10

This example relates to a magnetic recording medium using the structurehaving a phase-separated structure of the present invention forcontrolling a recording layer.

At first, the characteristic of the phase-separated structure of thestructure of the present invention originates from materials having aeutectic relationship over a wide temperature region. In other words,the materials have a simple eutectic phase diagram as shown in FIG. 4Cor 4D. The structure of the present invention is superior to thephase-separated structure in a currently used CoCr-based magneticrecording medium in variance of the average diameter of columnar membersand the like and shape of a columnar member. Furthermore, a layer regionwith disordered initial crystalline orientation or the like called theinitial layer of the recording layer 803 in a magnetic recording mediumof FIG. 8 has been found to adversely affect magnetic recording propertyor the like. The structure of the present invention is used as theunderlayer 802 to overcome this adverse effect. As a result, thecolumnar member portions of the structure each serve as a nucleus forcausing a magnetic particle of the recording layer 803 to start itsepitaxial growth from an initial stage of the formation of the recordinglayer. Thus, the recording layer 803 extremely excellent in control ofthe shape and crystallinity of a magnetic particle can be formed.

At first, a PdSi—Si system serving as the structure of the presentinvention is taken as a representative example, and is prepared as anunderlayer. Subsequently, a CoCrPt—SiO₂-based material is deposited bymeans of sputtering. The observation of the sample from a sectionaldirection by means of a transmission electron microscope can confirmthat PdSi forming a columnar member of the underlayer composed of thestructure of the present invention and CoCrPt forming a recording layerare epitaxially connected to each other to undergo crystal growth. Itcan be also confirmed that a SiO₂ portion grows in correspondence with aSi portion surrounding PdSi, so CoCrPt can form a recording layer whilethe variance of the diameter of PdSi in the underlayer is kept low. Thissituation is important in providing a low-noise magnetic recordingmedium.

As described above, the structure of the present invention can serve asan extremely excellent underlayer in crystal growth.

EXAMPLE 11

This example relates to a magnetic recording medium using the porousstructure of the present invention.

The porous structure of the present invention obtained in Example 6 isprepared. It should be noted that a metal layer composed of Pt is formedbelow the layer of the porous structure. The porous structure isimmersed in a plating solution mainly composed of cobalt sulfamate, anda voltage is applied through the Pt layer. A potential of −1.0 V isapplied to Ag/AgCl as a reference electrode. As a result, cobalt isdeposited from the bottom portion of each fine pore of the porousstructure. Therefore, a film having fine pores all of which are filledwith cobalt can be obtained. Thus, the fine pores of the porousstructure can be filled with a desired hard magnetic material by meansof a plating technique as long as a plating solution can be prepared. Atthat time, plating can be performed with a metal layer composed of alow-resistance metal arranged below the porous structure. Not onlyelectroplating but also electroless plating is found to be applicable.

As described above, a recording layer composed of a film filled with amagnetic material is formed. After that, diamondlike carbon is depositedto serve as a protective layer, and a lubricant composed ofperfluoropolyether is applied to form a lubricant layer. As a result, arecordable/reproducible medium can be obtained.

The magnetic recording medium thus obtained is resistant to alterationand impact in a use environment because a portion except the hardmagnetic particle portion of the recording layer is composed of acompound between the element A and Si_(n)Ge_(1-n) (where 0≦n≦1)excellent in strength.

In addition, the medium is extremely useful as a low-noise magneticrecording medium as well because magnetic particles are sufficientlyseparated. In particular, when the diameter of a magnetic particle isset to be 8 nm or less, a material mainly composed of an ordered alloysuch as CoPt or FePt is also available.

EXAMPLE 12

This example relates to a magnetic recording medium using the porousstructure of the present invention.

The porous structure of the present invention obtained in Example 6 isprepared. It should be noted that a metal layer composed of Pt is formedbelow the layer of the porous structure. The porous structure isimmersed in a soft magnetic plating solution mainly composed of nicklesulfamate and iron chloride, and a voltage is applied through the Ptlayer. A potential of −1.2 V is applied to Ag/AgCl as a referenceelectrode. As a result, a nickle-iron alloy is deposited from the bottomportion of each fine pore of the porous structure. Therefore, a filmhaving fine pores all of which are filled with the nickle-iron alloy canbe obtained. Thus, the fine pores of the porous structure can be filledwith a desired soft magnetic material by means of a plating technique aslong as a plating solution can be prepared. At that time, plating can beperformed with a metal layer composed of a low-resistance metal arrangedbelow the porous structure. Not only electroplating but also electrolessplating is found to be applicable.

As described above, a recording layer (one composed of CoCrPt—SiO₂-basedmaterial) is formed after the formation of a soft magnetic layercomposed of a film filled with a soft magnetic material. Furthermore,diamondlike carbon is deposited to serve as a protective layer, and alubricant composed of perfluoropolyether is applied to form a lubricantlayer. As a result, a recordable/reproducible medium can be obtained. Anunderlayer may be arranged between the soft magnetic layer and therecording layer.

The magnetic recording medium thus obtained is resistant to alterationand impact in a use environment because a portion except the softmagnetic particle portion of the soft magnetic layer is composed of asilicide excellent in strength.

In addition, the medium is extremely useful as a magnetic recordingmedium without spike noise or the like originating from a soft magneticlayer because soft magnetic particles are sufficiently separated.

EXAMPLE 13

This example relates to a magnetic recording/reproducing device usingthe magnetic recording medium of the present invention.

A device composed of a magnetic recording medium 1200, magneticrecording medium driving portion 1201, magnetic head 1202, magnetic headdriving portion 1203, and signal processing portion 1204 as shown inFIG. 12 is assembled by means of the magnetic recording medium of thepresent invention as shown in Examples 10, 11, and 12. As a result, amagnetic recording/reproducing device can be formed. This example doesnot limit the driving of the magnetic recording medium 1200 of thepresent invention to rotation and not limit the driving of the magnetichead 1202 to sliding on a circumference.

EXAMPLE 14

This example relates to an information processing system using themagnetic recording/reproducing device of the present invention.

Information can be output from/input to the magneticrecording/reproducing device portion 1301 shown in FIG. 13. Therefore,as shown in FIG. 13, an information processing system can be formed byhousing, in a housing container 1300, magnetic recording/reproducingdevice portion 1301, memory portion 1303, operating portion 1302,external input/output portion 1305, power source 1304, and wiring 1306for connecting them. The wiring 1306 plays its role as long asinformation can be exchanged irrespective of whether the wiring iscabled or wireless.

EXAMPLE 15

This example relates to a functional film having catalytic ability usingthe porous structure of the present invention. Here, a PtSi—Si-basedstructure is taken as a representative example of the structure of thepresent invention.

Four 15-mm square Pt plates were arranged on the center of a Sisputtering target, and sputtering was conducted at a substratetemperature of 300° C., an RF electric power of 120 W, and an argon gaspressure of 0.1 Pa. Thereby, a PtSi—Si-based structure having athickness of 1 μm was produced on the substrate 104 having a Wunderlayer. Then, the selective etching of a Si portion by means of anXeF₂ gas was conducted to confirm that a PtSi membrane is formed.Furthermore, an electrolyte film for a fuel cell can be applied andbonded under pressure, and peeled off. Thus, the PtSi membrane is peeledoff of the substrate 104 so that a functional film that can be used as acatalyst for a fuel cell can be formed, in which an electrolyte film1601 and a noble-metal-containing membrane 1603 are integrated with eachother as shown in FIGS. 16A (a plan view) and 16B (a sectional viewtaken along the line 16B-16B of FIG. 16A). The current density and fuelcell voltage property of the functional film are compared with those ofa catalyst obtained by causing carbon black to carry a general noblemetal particle (one caused to carry a noble metal has a thickness of 1μm) as a comparative example. It can be confirmed that the currentdensity of the functional film having catalytic ability of the presentinvention is about 2.5 times as high as that of the carrying catalyst asthe comparative example at the same voltage output. This indicates thata high current density can be obtained even when the amount of a noblemetal to be used per unit volume is small.

EXAMPLE 16

This example relates to a functional film having catalytic ability usingthe needle-like structure of the present invention. Here, aPtSi—Si-based structure is taken as a representative example of thestructure of the present invention.

Two 15-mm square Pt plates were arranged on the center of a Sisputtering target, and sputtering was conducted at a substratetemperature of 300° C., an RF electric power of 120 W, and an argon gaspressure of 0.1 Pa. Thereby, a PtSi—Si-based structure having athickness of 1 μm was produced on the substrate 104 having a Wunderlayer. Then, the selective etching of a Si portion by means of anXeF₂ gas was conducted to confirm that a PtSi rod is formed.Furthermore, an electrolyte film for a fuel cell can be applied andbonded under pressure, and peeled off. Thus, the PtSi rod is peeled offof the substrate 104 so that a functional film that can be used as acatalyst for a fuel cell can be formed, in which an electrolyte film1601 and a noble-metal-containing rod 1700 are integrated with eachother as shown in FIGS. 17A (a plan view) and 17B (a sectional viewtaken along the line 17B-17B of FIG. 17A). The current density and fuelcell voltage property of the functional film are compared with those ofa catalyst obtained by causing carbon black to carry a general noblemetal particle (one caused to carry a noble metal has a thickness of 1μm) as a comparative example. It can be confirmed that the currentdensity of the functional film having catalytic ability of the presentinvention is about 3 times as high as that of the carrying catalyst asthe comparative example at the same voltage output. This indicates thata high current density can be obtained even when the amount of a noblemetal to be used per unit volume is small.

EXAMPLE 17

This example relates to an electron emitting device using the structurehaving a phase-separated structure of the present invention.

As shown in FIGS. 18A (a plan view) and 18B (a sectional view takenalong the line 18B-18B of FIG. 18A), an insulation layer 1802 having anopening and a lead-out electrode 1803 are formed on the structure of thepresent invention having columnar members each composed of a compoundbetween the element A such as Nb, Mo, W, or Ti and Si_(n)Ge_(1-n) (where0≦n≦1). A voltage is applied between the lead-out electrode 1803 and thestructure of the present invention. It can be confirmed that the voltageapplication enables electrons to be efficiently released from thecolumnar members of the structure. In FIGS. 18A and 18B, referencenumeral 1801 denotes an electron emitting portion, and reference numeral1805 denotes a bias applying circuit. Furthermore, the following effectis obtained. That is, it can be confirmed that the columnar memberscomposed of the compound between the element A and Si_(n)Ge_(1-n) (where0≦n≦1) bring forth extremely high heat resistance. It can be alsoconfirmed that an electron emitting device having a long lifetime and astable current value upon electron emission can be obtained.

EXAMPLE 18

This example relates to an electron emitting device using theneedle-like structure of the present invention.

As shown in FIGS. 19A (a plan view) and 19B (a sectional view takenalong the line 19B-19B of FIG. 19A), an insulation layer 1802 having anopening and a lead-out electrode 1803 are formed on the structure of thepresent invention having columnar members each composed of a compoundbetween the element A such as Nb, Mo, W, or Ti and Si_(n)Ge_(1-n) (where0≦n≦1). Furthermore, selective etching by means of XeF₂ is performed toremove only the portion of Si_(n)Ge_(1-n) (where 0≦n≦1) around acolumnar member in a region corresponding to an electron emittingportion 1801, so a void portion 701 is formed. Then, a voltage isapplied between the lead-out electrode 1803 and the structure of thepresent invention. It can be confirmed that the voltage applicationenables electrons to be efficiently released from the columnar membersof the structure. Furthermore, the following effect is obtained. Thatis, it can be confirmed that the columnar members composed of thecompound between the element A and Si_(n)Ge_(1-n) (where 0≦n≦1) bringforth extremely high heat resistance. It can be also confirmed that anelectron emitting device having a long lifetime and a stable currentvalue upon electron emission can be obtained.

This application claims priority from Japanese Patent Application No.2005-088981 filed Mar. 25, 2005 and 2005-258274 filed Sep. 6, 2005,which is hereby incorporated by reference herein.

1. A structure comprising: a first member containing a compound between an element A and Si_(n)Ge_(1-n) (where 0≦n≦1); and a second member containing one of the element A and Si_(n)Ge_(1-n) (where 0≦n≦1), wherein one of the first member and the second member comprises a columnar member whose side face is surrounded by the other member, wherein the ratio Dl/Ds of an average diameter Dl in the major axis direction to an average diameter Ds in the minor axis direction of a transverse sectional shape of the columnar member is less than 5, and wherein the element A comprises one selected from the group consisting of Li, Na, Mg, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Rb, Sr, Y, Zr, Nb, Mo, Ru, Rh, Pd, Cs, Ba, La, Hf, Ta, W, Re, Os, Ir, Pt, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and B.
 2. A structure according to claim 1, wherein the average diameter in the minor axis direction in a plurality of the columnar members is in a range of from 0.5 nm to 20 nm.
 3. A structure according to claim 1, wherein an average distance between centers of gravity in a transverse sectional shape of each of a plurality of the columnar members and a columnar member closest thereto is 30 nm or less.
 4. A structure according to claim 1, wherein the structure has a shape of a film, and wherein the transverse sectional shapes in the columnar members are substantially identical to shapes of end faces of the columnar members forming one main surface of the film.
 5. A structure according to claim 1, wherein the structure has a eutectic alloy equilibrium diagram in the composition range between the first member and the second member.
 6. A magnetic recording medium comprising: an underlayer composed of the structure according to claim 1; and a recording layer which is arranged on the underlayer and contains magnetic particles dispersed therein, wherein the magnetic particles constituting the recording layer are positioned being connected to the columnar member of the underlayer in correspondence with the columnar member.
 7. A method of producing the structure according to claim 1, comprising the steps of: preparing a substrate; and forming a film on the substrate in a non-equilibrium state by means of a material individually or integrally containing Si_(n)Ge_(1-n) (where 0≦n≦1) and the element A, wherein, in the step of forming a film, a combination of a ratio of the Si_(n)Ge_(1-n) (where 0≦n≦1) to the element A and conditions upon formation of the film is used such that the ratio Dl/Ds is less than
 5. 8. A method of producing a structure according to claim 7, wherein the step of forming a film is performed by means of a sputtering method.
 9. A method of producing a structure according to claim 8, wherein a temperature of the substrate, a bias voltage to be applied to the substrate, a distance between a sputtering target and the substrate, input electric power, and a pressure of a process gas are selected as the conditions upon formation of the film.
 10. A method of producing a structure according to claim 7, further comprising the step of etching the columnar member to provide a porous structure.
 11. A method of producing a structure according to claim 7, further comprising the step of etching portions except the columnar member to provide a needle-like structure.
 12. A method of producing a magnetic recording medium comprising filling void portions of the porous structure according to claim 10 with a hard magnetic material to form a recording layer.
 13. A method of producing a magnetic recording medium comprising forming a recording layer and forming a soft magnetic layer by filling void portions of the porous structure according to claim 10 with a soft magnetic material. 